JRA3: Cold and Complex (Biomolecular) Targets

1
JRA3 Cold and Complex (Biomolecular) Targets
Co-ordinators Thomas Schlathölter and Reinhard
Morgenstern

• Why study interaction of HCI with biomolecular
  targets?
• Basic physics large energy transfer in a single
  collision!
• Applied physics HCI as secondary products, e.g.
  in radiation therapy

• Why cold targets?
• All molecules in one electronic (ground-) state
• Possibility of recoil momentum spectroscopy

2
Tasks and Volunteers
A. Solid biomolecular targets, CEA/Caen
(Huber, Lebius) B. Ionic biomolecular
targets NUI/Maynoth (ONeill, v.d. Burgt)
QUB/Belfast (Greenwood, Williams, McCullough,
OUL/London (Mason), KVI/Groningen (Schlathölter,
Morgenstern) C. Neutral gasphase biomolecular
targets CUB/ Bratislava
(Matejcik), OUL/London (Mason), UIBK/Innsbruck
(Scheier, Märk), LCAR/Toulouse (Moretto
Capelle) D. Ultracold neutral
targets (nanodroplets, MOTs) UBI/Bielefeld
(Stienkemeier, Werner), OUL/London (Mason),
KVI/Groningen (Schlathölter, Morgenstern) E.
Datareduction and analysis UBI/Bielefeld
(Werner),
3
A. Solid biomolecular targets
In the case of a nucleic bases, a compressed
powder is used as a 'solid' target, which can be
bombarded with ions of different charges and
energies, and at different incidence angles.
Fragmentation spectra are analysed with
mass-spectrometric methods.
DeOxyAdenosine
4
Dependence of the fragmentation of thymidine on
the incidence angle
(m241)
inset part magnified by a factor 10
Huber et al, Caen
5
B. Ionic biomolecular targets
Adaption of MALDI techniques
Desorption laser
Desorption of ions and neutrals
6
the principle to get an ionic target
3rd or 4th harmonic of our NdYAG-laser (355 or
266 nm) Quantel Brilliant pulse length 5 ns
frequency 50 Hz fluence up to 200 mJ/cm2 _at_
1064 nm.
MALDI and an electrostatic trap
7
trapped ions as target for HCI/fs-laser pulses
ECRIS or fs-laser
detector
reflectron
MALDI
sample
fields are switched off for MCI bunch passage!
trap
Einzel
lens
8
measurement cycle

• 1) laser desorbed ionic biomolecules are
  introduced from one electrode of the trap

1. ions pass a reflectron TOF spectrometer

reflectron
trap/TOF tandem leads to high mass resolution
which can be extended to high m/q values allowing
for the study of large biomolecules.
9
C. Neutral gasphase bio-molecular targets
Target production via evaporation possible for
DNA or RNA building bloks like thymine or uracil
Problem Are
the molecules in their electronic
groundstate? Approach for a solution
Check via reactions which are sensitive for
electronic state
Example H-loss or fragmentation in low energy
attachment reactions
10
Electron attachment (Scheier, Märk)
P. Scheier, T. Märk
M e? ? (M-H)? H
(0.33)
4
3
Cross section (10-20 m2)

2
1
0
0
1
2
3
4
Electron energy (eV)
11
D. Production and manipulation of ultracold
targets

• Capture in magneto-optical traps (MOTs)
• sympathetic cooling of molecules in a MOT
• Capture of biomolecules in He nano droplets

12
Ultra cold Na target in a Magneto Optical Trap
(MOT)
near resonance laser light to trap and cool Na
atoms
13
TOF and recoilspectroscopy of O6 Na collisions
14
Apparatus for He nanodroplet studiesToennies et
al , Physics Today, Feb. 2001, 31-37
15
Helium droplet beam machine
Fakultät für Physik
16
Formation of large molecular complexes in helium
droplets
Formation of large molecular complexes in helium
droplets
Spectroscopy of excitonic transitions in PTCDA
nanostructures at 380 mK
M. Wewer and F. Stienkemeier, Phys. Rev. A 37,
2002
17
Laser induced fluorescence spectrum of PTCDA
(a) in a nanodroplet (b) in the gasphase F.
Stienkemeier and A.F. VilesovJ. Chem. Phys.115
(2001) 10119
18
E. Data reduction and analysis
A non-trivial task! High-dimensional parameter
space! (up to 30-40 parameters per
collision event) Pattern recognition Fitting
procedures based on e.g. maximum entropy methods
19
Fragmentation of thymidine by ions with high and
low charge
Xe20, 400 keV
O2, 40 keV
Huber et al, Caen NIM B 205 (2003) 666670